Preferred indoor lighting features depends on room characteristics such as size and color. Lighting is also affected by positioning of the luminaire(s), such as height of an edgelit luminaire in a room.
Edgelit luminaires are configured to deliver light upward and downward at a single up/downlight ratio. These systems are thus limited to providing only one pre-defined direct/indirect lighting quality. An example ratio is fifty percent uplight, fifty percent downlight.
A generally fifty/fifty (50%/50%), or half-half, up/down luminaire could produce ideal lighting for a particular room characteristic (e.g., size, or color) and luminaire positioning. If the room has other characteristics, and/or the luminaire must be positioned otherwise, such as for architectural or decorating reasons, the same luminaire will not produce ideal lighting.
In some cases, re-positioning the luminaire can improve the lighting. This is not possible in all cases, though. When possible, the re-positioning may require a good amount of work (cost), and still the resulting position may not be preferred from an architectural or design standpoint.
Another option, when a particular edgelit luminaire and luminaire positioning are not conducive for a particular room, is to obtain a different luminaire, with its added cost.
A designer looking to use luminaires in each of twenty different rooms of a building, for instance, may need to purchase twenty different types of edgelit luminaires, which can be much more expensive than ordering the same type in bulk. Or a basic renovation of a room having edgelit luminaires can require purchase of new luminaires.
Still another option, when a particular edgelit luminaire and luminaire positioning are not conducive for a particular room, is to use baffles or plates to block select amounts of up and/or down light from a fixed ratio luminaire to change the uplight/downlight ratio effectively. This arrangement, though, has negative impacts on optical efficiency. Less light is emitted from the system, for instance, representing wasted energy and usually less than idea lighting from the lumen power available for the fixture.